Push to talk over cellular, PoC, is a half-duplex, bidirectional, instant, and multiparty communication technology based on public cellular mobile communication networks and provides a user with group session services of multimedia for communication with one or more parties. PoC service is similar to walkie-talkie services in which a user pushes a button to talk to another user or to broadcast to the terminal of the group participants; after the initial voice, other participants may respond to the voice message. Because the PoC communication is half-duplex, only one participant is allowed to speak each time while the other participants are listening. A PoC work team has been established officially by Open Mobile Alliance, OMA, in April, 2003 to constitute the standards of the PoC system structure. In the PoC service, a significant function is to provide the storing and broadcasting services when the user is unable to take part in a session. Therefore, the message that the user wishes to broadcast during the session without his presence may be pre-stored and broadcasted later, while the conversation made by other users may also be stored and broadcasted to the user when the session is over. In order to implement the storing and broadcasting of the session, PoC develops a PoC message storing function, i.e. PoC Box, taking the place of the user in the session by broadcasting the pre-stored message and storing the content of the session.
Users may communicate with a PoC storing module having PoC Box via a terminal with PoC function, and upload message the user wishes to broadcast during the session. Further, users may communicate directly with a PoC storing module, listen to the message recorded during the session PoC storing module takes part in and perform management operations, such as deletion, on data. Each user corresponds to a PoC storing module, and different identifiers may be used to identify PoC storing modules of different users.
Network PoC message storing function, i.e. NW PoC Box, is specified in PoC 2.0 by OMA as follows: the PoC server and Session Initiation Protocol/Internet Protocol (SIP/IP) CORE are respectively connected with the PoC storing module having PoC Box via the PoC11 and 12 interfaces. The PoC 11 interface supports communication between the network PoC storing module and SIP/IP CORE and employs the SIP protocol. PoC 12 interface is an interface between the PoC storing module and PoC server, and employs Real time Transport Protocol (RTP) and Real time Transport Control Protocol (RTCP). PoC terminal may communicate with a PoC server and a PoC storing module, respectively, via PoC 11 and 12 interfaces to implement functions of leaving message, broadcasting message, inviting the PoC storing module to take part in the session, and managing PoC Box data, etc.
The PoC Box provided in the PoC service may provide session storing and broadcasting service in a session; however, because of the immaturity of the PoC Box, all infrastructures need to be newly established if the PoC Box is to be applied, which increases investment and causes a great waste. Currently, no solution is available for implementing PoC session storing and broadcasting as well as reducing the investment.